Fire-insulating wall covering and a preparation method for same

ABSTRACT

The invention relates to a sound-absorbing and fire-insulating wall covering, comprising a cured mixture of: (i) 5-20% by weight mineralized wood fibre; (ii) 20-60%/o by weight sand with an SiO2 content of less than 5% by weight and a greywacke content of at least 30% by weight; and (iii) 20-50% by weight cement, and to a method of preparing a fire-insulating wall covering, wherein relative to the cured weight are mixed 5-20% by weight mineralized wood fibre, 30-60% by weight sand with an SiO 2  content smaller than 5% by weight and a greywacke content of at least 30% by weight, and 20-50% by weight cement, and 10-30% by weight water is then added, whereafter the mixture is cured to form the fire-insulating wall covering.

The present invention relates to a fire-insulating wall covering and toa method for preparing same. The present invention relates particularlyto a fire-insulating and preferably also sound-absorbing wall coveringwhich meets currently stringent requirements in respect offire-insulating properties. Such a fire-insulating wall covering can beapplied in tunnels, underground spaces such as shopping centres and thelike.

Fire-insulating wall coverings known at the present time do not fullysatisfy the stringent requirements in respect of fire-insulatingproperties. In the case of a fire load on such a wall covering, forinstance for 120 minutes, and a temperature on the fire side lying inthe range of 1100 to 1350° C. for these two hours, these fire-insulatingproperties mean, among other things, that this wall covering insulatesagainst fire such that on the side of the wall covering remote from thefire the temperature remains relatively low, and particularly below 225°C., preferably below 200° C.

The wall covering must moreover have good sound-absorbing properties andis asbestos-free.

The invention has for its object to provide such a fire-insulating andsound-absorbing wall covering as well as a method for preparationthereof. It is noted here that the wall covering can be applied per se,but is preferably applied as wall covering arranged on a supportinglayer, for instance a concrete layer which can optionally bestrengthened with a reinforcement. The underlying layers are thusprotected against high temperatures.

This is achieved according to the invention with a fire-insulating wallcovering comprising a cured mixture of:

-   -   i) 5-20% by weight mineralized wood fibre;    -   ii) 20-60% by weight sand with an SiO₂ content of less than 5%        by weight and a greywacke content of at least 30% by weight; and    -   iii) 20-50% by weight cement.

The fire-insulating wall covering is in fact based on a cured cementplate having incorporated therein a specific type of wood fibre and aspecific type of sand.

The applied wood fibre for inter alia sound absorption is a mineralizedwood fibre. Such a mineralized wood fibre is obtained by bringing woodfibres into contact with a solution of aluminium sulphate. The woodfibres are generally obtained from residual wood which is processed indifferent steps to form wood fibre with a moisture content of about15-25% (atro basis). The aluminium sulphate is added in a quantity ofabout 2.5% relative to the wood fibre and supplemented with a quantityof water, whereby the moisture percentage rises to about 100% (atro).The obtained wood fibres, which are thus covered with aluminiumsulphate, are the mineralized wood fibres applied in the fire-insulatingwall covering according to the invention.

The applied aluminium sulphate is of standard chemical quality.

The sand is a specific sand type since it is less than 5% by weightSiO₂. The sand further contains at least 30% by weight greywacke.Greywacke is a type of stone containing feldspar, apatite and the like.Clay mineral may also be present. It is a clastic sedimentary rock witha density of for instance 2.6 kg per m³. The greywacke can be applied indifferent grain size distributions (or combinations), where the grainsize distribution is such that the average particle size can be around 1mm, 4-8 mm, 11-16 mm.

The cement used is generally a portland cement, in particular a portlandslag cement.

For an optimum fire-resistant property the wall covering preferably hasa content of mineralized wood fibre of preferably 7-15% by weight, morepreferably 10-15% by weight. By selecting the content of mineralizedwood fibre subject to the desired properties, not only is an optimumfire-resistant property obtained but also an optimum sound-insulatingproperty. It is striking in this respect that use is made of a componentbased on wood fibre to obtain fire-resistant properties.

The fire-insulating wall covering preferably contains 35-50% by weightsand, while the SiO₂ content is preferably lower than 2.5% by weight,more preferably lower than 2% by weight. By opting for a relatively lowSiO₂ content in combination with an optimal choice of the quantity ofgreywacke, (preferably at least 50% by weight), optimum fire-insulatingproperties are obtained and the fire breakthrough can be extended a verylong time and far beyond the test time (2 hours).

A fire-insulating wall covering is-found to suffice well in practice ifit preferably contains

-   -   i) 10-15% by weight mineralized wood fibre;    -   ii) 35-50% by weight sand with an SiO₂ content smaller than 2%        by weight and a greywacke content greater than 50% by weight;        and    -   iii) 25-40% by weight cement.

The best properties are obtained if in this case the cement is alow-chromate cement.

The fire-insulating and fire-resistant properties of the wall coveringcan be further improved if the mineralized wood fibres and/or the sideof the wall covering to be exposed are provided with an impregnationwhich further improves the fire resistance and/or the durability of woodfibres. Such an impregnating agent is for instance the impregnatingagent described in the German patent application 197 27998. Thisimpregnating agent is preferably applied to the mineralized wood fibresin a quantity of 0.1-1% by weight, more preferably 0.1-0.5% by weight.In the case the wall covering is arranged on a wall to be exposed, it isrecommended to apply the impregnating agent in a quantity of 30-500 gramper m², preferably 100-250 gram per m².

The fire-insulating wall covering according to the invention can inprinciple be formed on-site and cured on-site in a mould. It is howeveralso possible for pre-cured plates to be taken to the location of use.

If the fire-insulating wall covering has an insufficient strength initself and insufficient bearing capacity, it is recommended to arrangesuch a fire-insulating wall covering on a supporting layer, for instancea concrete layer or concrete plate.

In that case the fire-insulating wall covering can be formed on analready present concrete plate and attached thereto using connectingmeans. Another option is to arrange finished fire-insulating wallcoverings on a prepared support layer using fixing means. Use is made inthis case of openings arranged in the fire-insulating wall covering forarranging the fixing means and of plugs of fire-insulating wall coveringto cover the fixing means.

In the case that a plurality of plates of fire-insulating wall coveringaccording to the invention are applied, this results in joints. Foroptimal retention of the fire-insulating properties at the position ofthe joint, it is recommended to make use of an offset joint and to fillthis joint with either fire-insulating wall covering in uncured form orwith another fire-insulating seal.

A good fire-insulating wall covering is generally obtained according tothe invention if relative to the cured weight are mixed 5-20% by weightmineralized wood fibre, 30-60% by weight sand with an SiO₂ contentsmaller than 5% by weight and a greywacke content of at least 30% byweight; and 20-50% by weight cement, and 10-30% by weight water is thenadded, whereafter the mixture is cured to form the fire-insulating wallcovering. Wall thicknesses of 10 to 500 mm are generally possible.

Mentioned and other features of the fire-insulating wall coveringaccording to the invention and of the method for preparing such afire-insulating wall covering will be further elucidated hereinbelowwith reference to two embodiments, which are only given by way ofexample without the invention being deemed limited thereto.

FIGS. 1 and 3 each show a perspective view of a space provided with afire-insulating wall covering; and FIGS. 2 and 4 each show across-section at the position of details II and IV respectively of FIGS.1 and 3.

For the preparation of the fire-insulating wall covering, use is madeper m³ of:

12% by weight mineralized wood fibre

32% by weight portland slag cement

42% by weight sand (SiO. content smaller than 5% by weight, greywackecontent 42% by weight)

0.01% by weight pigment (chromium oxide)

0.1% by weight impregnating agent (DE 197 27998)

residual water.

This mixture is placed in a mould provided with profiles, recesses forfixing points, rebates and joints. The mass is vibrated, pressed andfinally released onto a ground in order to cure. The formed plate isoptionally sprayed at this moment with impregnating agent. Such a plateis applied in the embodiment shown in FIGS. 1 and 2.

In another embodiment the fire-insulating wall covering according to theinvention for curing is arranged, for instance in a curved mould, onto asupport layer of concrete already arranged therein. After curing thesestructural parts can be applied in for instance the embodiment accordingto FIGS. 3 and 4.

In another embodiment, preformed fire-insulating wall coveringsaccording to the invention are placed in a mould after being providedwith coupling means for coupling to the concrete layer to be arranged.Use is for instance made of wood screw bolts which protrude out of thesurface and which will be taken up in the concrete layer to be arrangedon this wall covering. Via the coupling means an optimal attachment isthus obtained between the concrete layer on the one hand and the wallcovering according to the invention on the other.

FIG. 1 shows a tunnel 1 provided with a concrete bearing structure 2with fire-insulating wall coverings 3 according to the invention fixedthereto. Fixing means 4 are covered with conical plugs 5. Wall coverings3 are mutually separated by a joint 6.

FIG. 2 shows a detail in cross-section of the structure of this tunnelwall which is provided with wall coverings 3 according to the invention.Wall covering 3 is arranged in the concrete bearing structure 3 usingfixing means 4, in this case cotter bolts 7. This bearing structure 3 isfurther provided with a reinforcement 8.

As shown in FIG. 2, joint 6 is an offset joint which is filled, whollyor only in the two straight joint parts, with a fire-insulating seal 9,optionally a mass of the insulating wall covering according to theinvention still to be cured.

FIGS. 3 and 4 show a pedestrian passage 10, for instance in anunderground station. Use is made in this case of wall plates 12 and 13which are preformed and set up in situ. Wall plates 12 and 13 once againcomprise a concrete support structure and a wall covering 14 accordingto the invention. Wall covering 14 is provided with wood screw bolts 15onto which is poured the concrete bearing structure 11, which is alsoprovided with a reinforcement 8.

In both cases the wall coverings 3 and 14 according to the invention arefound to satisfy the stringent requirements made in respect offire-insulating properties. When exposed to a temperature regime asaccording to the table below, it was found that on the side of such a100 mm wall covering remote from the fire the temperature remains below120° C., and is even close to a temperature lying between 100 and 110°C. Time Temperature (min) (° C.) 0 20 3 890 5 1140 10 1200 30 1300 601350 90 1300 120 1200

1-10. (canceled)
 11. A fire-insulating wall covering, comprising a cured mixture of: i) about 5 to about 20% by weight mineralized wood fibre; ii) about 20 to about 60% by weight sand with an SiO₂ content of less than about 5% by weight and a greywacke content of at least about 30% by weight; and iii) about 20 to about 50% by weight cement.
 12. A wall covering as claimed in claim 11, containing about 7 to about 15% by weight-mineralized wood fibre.
 13. A wall covering as claimed in claim 12, containing 10-15% by weight mineralized wood fibre.
 14. A wall covering as claimed in claim 12, containing about 35 to about 50% by weight sand.
 15. A wall covering as claimed in claim 14, wherein the sand has an SiO₂ content less than about 2.5% by weight.
 16. A wall covering as claimed in claim 15, wherein the sand has an SiO₂ content less than 2% by weight.
 17. A wall covering as claimed in claim 15, wherein the sand contains at least about 40% by weight greywacke.
 18. A wall covering as claimed in claim 17, wherein the sand contains at least 50% by weight greywacke.
 19. A wall covering as claimed in claim 17, containing about 25 to about 40% by weight cement.
 20. A wall covering as claimed in claim 19, containing: i) about 10 to about 15% by weight mineralized wood fibre; ii) about 35 to about 50% by weight sand with an SiO₂ content less than about 2% by weight and a greywacke content greater than about 50% by weight; and iii) about 25 to about 40% by weight cement.
 21. A wall covering as claimed in claim 20, wherein the cement is low-chromate.
 22. A wall covering as claimed in claim 21, containing about 0.1 to about 1% by weight-impregnating agent.
 23. A wall covering as claimed in claim 22, containing 0.1-0.5% by weight impregnating agent.
 24. A wall covering as claimed in claim 21, containing about 30 to about 500 grams per m impregnating agent.
 25. A wall covering as claimed in claim 24, containing 100-250 grams per m² impregnating agent.
 26. A wall covering as claimed in claim 11, containing about 35 to about 50% by weight sand.
 27. A wall covering as claimed in claim 11, wherein the sand has an SiO₂ content less than about 2.5% by weight.
 28. A wall covering as claimed in claim 27, wherein the sand has an SiO₂ content less than 2% by weight.
 29. A wall covering as claimed in claim 11, wherein the sand contains at least about 40% by weight greywacke.
 30. A wall covering as claimed in claim 29, wherein the sand contains at least 50% by weight greywacke.
 31. A wall covering as claimed in claim 11, containing about 25 to about 40% by weight cement.
 32. A wall covering as claimed in claim 11, containing: i) about 10 to about 15% by weight mineralized wood fibre; ii) about 35 to about 50% by weight sand with an SiO₂ content less than about 2% by weight and a greywacke content greater than about 50% by weight; and iii) about 25 to about 40% by weight cement.
 33. A wall covering as claimed in claim 11, wherein the cement is low-chromate.
 34. A wall covering as claimed in claim 11, containing about 0.1 to about 1% by weight impregnating agent.
 35. A wall covering as claimed in claim 34, containing 0.1-0.5% by weight impregnating agent.
 36. A wall covering as claimed in claim 11, containing about 30 to about 500 grams per m² impregnating agent.
 37. A wall covering as claimed in claim 36, containing 100-250 grams per m² impregnating agent.
 38. A method of preparing a fire-insulating wall covering comprising a cured mixture of: i) about 5 to about 20% by weight mineralized wood fibre; ii) about 20 to about 60% by weight sand with an SiO₂ content of less than about 5% by weight and a greywacke content of at least about 30% by weight; and about 20 to about 50% by weight cement; wherein relative to the cured weight are mixed about 5 to about 20% by weight mineralized wood fibre, about 30 to about 60% by weight sand with an SiO₂ content less than about 5% by weight and a greywacke content of at least about 30% by weight, and about 20 to about 50% by weight cement, and about 10 to about 30% by weight water is then added, whereafter the mixture is cured to form the fire-insulating wall covering. 